This invention relates to improvements in power transmission belts. In one aspect this invention relates to an improved power transmission belt. In another aspect it relates to a method for making an improved power transmission belt. In yet another aspect, this invention relates to an improved power transmission system.
Belt-driven power transmission systems are widely used. In general such systems are coplanar, i.e., the driving and driven pulley sheaves are arranged in a single plane. Power transmission systems wherein the pulley sheaves are not coplanar are also known. For example, the system disclosed in U.S. Pat. No. 3,774,464 comprises an upright drive pulley, apair of spaced, upright mule guide pulleys, a plurality of spaced, coplanar, driven pulleys mounted for rotation about upright axes, and a single, continuous belt trained around the pulleys and having a single arc of contact with each pulley. Although not specified, this belt appears in the drawings to be of the V-type.
The power transmitting advantages of a V-belt as compared with flat belts and round belts are well known in the art. A V-belt wedges into a pulley groove and can transmit power even under conditions where a flat or round belt might not.
As noted previously, V-belts are generally used in coplanar drive systems. When used in multi-planar systems, such as that disclosed in U.S. Pat. No. 3,774,464, the belt must be twisted to assure that the belt will be properly positioned in the various pulley grooves. During operation, particularly high speed operation, should the belt enter the pulley at the wrong attitude, the belt will either fail to properly transmit power, or will flip off of the pulley.
A solution to the problem of belt slippage is provided by U.S. Pat. No. 2,347,798 which discloses a drive belt having a plurality of working surfaces, any pair of which can be used for transmitting power employing the wedging action normally associated with a V-belt. This belt preferably has an equilateral triangular cross-sectional shape, and comprises an equilateral triangular cord of relatively inextensible cords embedded in rubber, and superimposed rubberized fabric layers applied around the cord. This triangular belt is superior to a V-type belt in that a plurality of working surfaces are available rather than the two working surfaces of a V-type belt. However, the triangular belt is prone to flipping off of a pulley, just as is a V-type belt, if it enters a pulley at the wrong attitude.
The triangular belt disclosed in U.S. Pat. No. 2,347,798 is also superior to a round belt, since a round belt does not provide the wedging action required to prevent slipping of the belt during use. A round belt, however, has no attitude at which it must enter a pulley groove. What is desired, therefore, is an endless power transmission belt which combines the wedging action of a V-type or polygon shaped belt with the reduced tendency to flip out of a pulley groove of a round belt.
It is therefore an object of the present invention to provide an improved endless power transmission belt which provides the advantages of a V-type belt combined with the advantages of a round belt.
It is another object of the present invention to provide a method for producing an improved endless power transmission belt.
It is a further object of the present invention to provide an improved multi-planar power transmission system.
Other objects, aspects and advantages of the present invention will be apparent to those skilled in the art from the following description taken with the attached drawings.